CHARACID FISHES — WEITZMAN 



29 



British Guiana specimens 3.4-3.6]; eye in head 3.0 (2.9-3.1); snout 

 in eye 1.0 in all specimens examined; least width of bony interorbital 

 in greatest eye diameter 1.0 in all specimens. 



Premaxillary with 7 quinquecuspid teeth, lateroposterior cusp 

 largest. Maxillary having 1 tooth with 4 or 5 cusps. Dentary with 

 8 sexcuspid teeth, cusps subequal and central cusps longest; 11 teeth 

 in second row of dentary in alizarin specimens. Gill rakers 9 + 13. 



Dorsal fin rays ii,8; anal iii,9; pectoral i,9 to i,10; pel vies iii,7. 

 Adipose fin present in all specimens examined but reduced in size in 

 some. Caudal fin with principal rays 10/9; distal tips of all elements 

 of first 10 principal rays in upper caudal lobe. Lower caudal lobe 

 with all elements of remaining 9 principal rays. 



.^-^^ 



kT/NM^ 



Figure 7. — Nannostomus trifascialus, male, SL 27.5 mm., SU 36899. 



Anal fins of male and female appear alike in this species; rays of 

 male's anal fin not modified. Inclinator muscles appear slightly, if 

 at all, more developed in male than in female. 



Radial grooves of scales belonging to third horizontal scale series 

 and lying below dorsal fin are shown in figure 7. Posterior field with 

 1 or 2 radial grooves. Dorsal and ventral fields each with 1 radial 

 groove and anterior field with 2 to 4 radial grooves. Scales in a 

 lateral series 26 to 27; 3 to 5 lateral-Hne scales and 10 scales in median 

 series anterior to dorsal fin. Total number of vertebrae 35 to 36, 

 19 precaudal and 16 or 17 caudal vertebrae. 



Color in alcohol. — Top of head light to dark brown. Primary 

 horizontal stripe extending on head from snout tip and lower jaw 

 posteriorly over first orbital bone across eye and operculum, termi- 

 nating at posterior border of operculum. On body, primary horizontal 

 stripe extending from under fleshy flap of opercle through fourth scale 



